Ethernet Provides the Solution for Broadband Subscriber Access
Chapter 2: Layered Architecture & Applications · Fast Ethernet provides 100MB/s, Gigabit Ethernet...
Transcript of Chapter 2: Layered Architecture & Applications · Fast Ethernet provides 100MB/s, Gigabit Ethernet...
CHAPTER 2: LAYERED
ARCHITECTURE, NETWORK
CLASSIFICATION & APPLICATIONS
Dr. Bhargavi Goswami
Department of Computer Science
Garden City College of Science & Management Studies.
9426669020
APPROACHES TO NETWORK DESIGN:
TOPDOWN APPROACH
DEFINITION
A computer network can be defined as a
collection of computing devices (nodes)
interconnected by wires or wireless means and
governed by a set of standards (protocols) in order
to share data and resources.
CATEGORIZE NETWORKS BASED ON
MULTIPLE FACTORS
1. Division based on Scope
2. Division based on Connection
3. Division based on Communication
4. Division based on Usage
1. DIVISION BASED ON SCOPE
PAN or Personal Area Network or the wireless
version WPAN (Wireless PAN)
LAN or Local Area Network which is usually
confined to a moderately large building.
MAN or Metropolitan Area Network which is
confined to a city or a part of it.
WAN or Wide Area Network which can span
multiple countries.
Scope
PAN LAN MAN WAN
TWO IMPORTANT MECHANISMS
What if congestion exist for line where packet is to be sent? Router stores that packet until congestion is resolved and once resolved, it forwards packets to that line. This is called Store & Forward Subnet.
A stream of packets from sender to receiver. Packets follow route ACE, rather than ABDE or ACDE. Some n/w predetermine route that is to be followed. First decision is taken by A with the help of some routing algorithm and then by C. All WANs are not packet switched. See next figure.
Store & Forward Packet Switched Subnet
2. DIVISION BASED ON CONNECTION
Need some sort of cables for connectivity.
Most popular are UTP (Unshielded Twisted Pair) and Fiber Optics.
Fast Ethernet provides 100MB/s, Gigabit Ethernet provides 1Gbps/s, 10G provides 10Gbps/s and 40/100G would come to Indian market soon.
Fiber Optics provides nearly 5000 Times more bandwidth of conventional telephone cables.
First wireless network was ALOHA.
Ethernet is successor of ALOHA.
Other networks like Wi-Fi (802.11), Wireless Fidelity providing LAN Interpretability is widely accepted wireless networks.
WiMax (802.16) wireless microwave access is covering large area of entire city.
Wired Wireless
MANETS
i) MANets:
Mobile Ad Hoc Networks
Nodes can come and join at their own will and leave on their own will.
Services Provided are as follows:
One can access internet from hotel by joining hotel network
One can join network of railway station with session of 15 minutes
Student can access network of college from parking area or lobby
We can use internet during flight n share the files with co-passengers.
Students can exchange class notes without writing it manually.
Issues in MANets:
Topology is dynamic
Power Consumption is important concern for mobile nodes. When A is communicating with C through intermediate node B, if the battery of B is low, it would not forward packets of A to C.
Security must be more stringent with such networks as we expect guest to join the network any time.
War Driving: It is a common Mechanism deployed by hackers to join wireless networks and extract information that is vital. This process is described as War Driving.
SENSORS
ii) Sensor Networks:
Sensor Networks are special type of Ad Hoc
Networks, where the members of this network
are tiny sensors rather than mobile computers or
large devices.
Sensors are sometimes mobile and sometimes
stationary.
Eg. Temperature Sensors detect temperature and
sends it to some other nodes.
Sensors are designed with much less memory and
processing power is also too small.
3) DIVISION BASED ON
COMMUNICATION TYPE
Communication Type
Point to Point
MulticastBroadcast
BROADCAST
BROADCAST
BROADCAST
Better when a very low probability of more than one user transmitting simultaneously
It is useful when the network is inherently a broadcast network.
Better when routing through neighbours or addressing each node of the network is not required
Broadcasting helps when the topology is not fixed.
POINT TO POINT
POINT TO POINT
POINT TO POINT
P2P requires to know where the recipient is
Sender must know where each router is
Similarly each router must be aware of where
other routers are located
For inherently broadcast network P2P
communication is not possible.
Little advantage for high bandwidth case
MULTICAST
One sender, multiple receivers, but, not all.
Switch is the device that provides this facility.
4. DIVISION BASED ON USAGE
HOME
SENSORS
OTHERS
HOME NETWORKS
Smart spectacles helps old people
Smart Keys
A phone receiver transfers the call automatically
Control house via Internet or phone.
The shower adjusts the temperature
Single remote control for many home devices
ISSUES:
Robustness
Cost
Security issues
Regular upgrades
Maintenance and availability
Wired or Wireless
Holding the vendor responsible
SENSORS
b) Sensor Networks:
Used for specific purpose like monitoring a process or recording the outcomes of continuous experiment.
What is the need of sensor networks?
Fire erupts in a warehouse in an industry can call fire brigade.
If sudden rainfall in Delhi (Bangalore always have rainfall) , can cause adverse effect to the farm, to what extent of humidity is there in the farm, can be determined by sensor networks
After the earthquake, building with sensors can monitor record vibration data to confirm that structure is safe to enter.
Sensor networks have large number of nodes.
Sensor networks have no fixed topology.
Sensor nodes have less memory and processing power.
Sensors are usually very small.
Sensor can be immobile.
Size, power and memory all, low.
Sensor may not be individually addressable.
Power consumption is crutial in Sensors
Sensor nodes may captured, stolen.
OTHER NETWORKS
Pervasive computing and research on wearable computers are helping.
Pervasive networking means, if you are out on vacation, all the emails are copied to yr outlook and they are msged that u r on vacation.
Wearable computers are those which can be worn on the body like a dress.
Microprocessors are also the example for it.
Passive Environment becomes Active: eg. U enter the room and light automatically switches on and light music starts playing.
In today’s scenario, toll booth have long queues. But if we have sensors, RFID can just pass by, all the details are recorded, and toll is deducted from the RFID card.
Phones are used to check emails and computers answer the phone calls.
NETWORK COMPONENTS
The Network Interface Card
Cable for wired connection
Frequency band for wireless transmission
The servers and the nodes
Interconnecting Devices
i) Hubii) Switchiii) Repeateriv) Bridgev) Router
Network Components
NIC
Cable
Frequency Band
Hub
SwitchRouter
Bridge
Repeater
End Host
DEFINITIONS
NIC: The first requirement of connectivity at node’s end is Network Interface Card NIC or LAN Card. Eg. Ethernet Card (Wired ) and Centrino Card (Wireless).
Cables for Wired Communication: There is a LAN cable slot in motherboard on which network cable fits. Cables can be for different types. Eg. UTP (Cat 3,5,6,7), Copper Cable (Thin and Thick) and Fiber Optics.
Frequency Band for Wireless Communication: More the frequency more is the data rate. Rights has to be taken from Government of India, body DoT (Department of Telecommunication) to transmit data using frequency.
Servers and Nodes: Networking machine in networking parlance is known as a node or host. We have LAN card and wire to connect. Nodes giving service is server and nodes demanding service is client.
DEFINITIONS
Interconnecting Devices: It’s not possible to get
connected to every client directly. So we need some
interconnecting device that connects each of us.
Hub: A Hub is an intermediate device that connects
to server with its clients through wires. It has
multiple ports. It is broadcast by nature. Impose
network load as do not store addresses of
communicating clients to its memory.
Switch: Switch is an interconnecting device that
supports P2P communication in a local network.
Switch stores the information of its connected nodes
in its buffer so that it can utilize it for point to point
communication. It reduces network load.
DEFINITIONS
Repeater: Signal’s strength reduces gradually by covering the distance. The device that reshapes the digital signal is called a repeater. For this, Amplifiers are needed by analog signals. Repeaters also remove noise from the digital signals which is not done by amplifiers for analog signals.
Bridge: Special device called bridge is used to connect more networks. A bridge is similar to switch but is designed to provide additional services like broadcasting in a particular LAN segment, finding out the shortest path between different LAN segments. A bridge keeps broadcast in network limited to that network only. It keeps, logically separate segments physically separate. Bridge operates upon Data Link Layer.
DEFINITIONS
Router: A router is a device or, in some cases, software in a computer, that determines the next network point to which a packet should be forwarded toward its destination. A router may create or maintain a table of the available routes and their conditions and use this information along with distance and cost algorithms to determine the best route for a given packet.
Gateway: Gateways are conventionally used to connect the networks. It operates on higher layers like transport layer and application layer. It provide an application seamless access to remote networks. Eg. Proxy Server. Two types of gateways are there. 1) Transport gateway: connect two computers using different connection-oriented transport protocols (TCP, ATM). 2) Application gateway: translate format and contents of data. E.g., email gateway: translate Internet message into SMS for mobile phones.
NEED FOR PROTOCOL ARCHITECTURE
data exchange can involve complex procedures,
cf. file transfer example
better if task broken into subtasks
implemented separately in layers in stack
each layer provides functions needed to perform
comms for layers above
using functions provided by layers below
peer layers communicate with a protocol
KEY ELEMENTS OF A PROTOCOL
syntax - data format
semantics - control info & error handling
timing - speed matching & sequencing
TCP/IP PROTOCOL ARCHITECTURE
developed by US Defense Advanced Research Project Agency (DARPA)
for ARPANET packet switched network
used by the global Internet
protocol suite comprises a large collection of standardized protocols by the Internet Activities Board (IAB).
SIMPLIFIED NETWORK ARCHITECTURE
TCP/IP LAYERS
no official model but a working one
Application layer
Host-to-host, or transport layer
Internet layer
Network access layer
Physical layer
PHYSICAL LAYER
concerned with physical interface between computer
and network
concerned with issues like:
characteristics of transmission medium
signal levels
data rates
other related matters
NETWORK ACCESS LAYER
exchange of data between an end system and attached network
concerned with issues like :
destination address provision
invoking specific services like priority
access to & routing data across a network link between two attached systems
allows layers above to ignore link specifics
INTERNET LAYER (IP)
routing functions across multiple networks
for systems attached to different networks
using IP protocol
implemented in end systems and routers
routers connect two networks and relays data
between them
TRANSPORT LAYER (TCP)
common layer shared by all applications
provides reliable delivery of data
in same order as sent
commonly uses TCP
APPLICATION LAYER
provide support for user applications
need a separate module for each type of
application
OPERATION OF TCP AND IP
ADDRESSING REQUIREMENTS
two levels of addressing required
each host on a subnet needs a unique global
network address
its IP address
each application on a (multi-tasking) host needs a
unique address within the host
known as a port
OPERATION OF TCP/IP
TRANSMISSION CONTROL
PROTOCOL (TCP)
usual transport layer is (TCP)
provides a reliable connection for transfer of data between applications
a TCP segment is the basic protocol unit
TCP tracks segments between entities for duration of each connection
TCP HEADER
USER DATAGRAM PROTOCOL
(UDP)
an alternative to TCP
no guaranteed delivery
no preservation of sequence
no protection against duplication
minimum overhead
adds port addressing to IP
UDP HEADER
IP HEADER
IPV6 HEADER
TCP/IP APPLICATIONS
have a number of standard TCP/IP applications
such as
Simple Mail Transfer Protocol (SMTP)
File Transfer Protocol (FTP)
Telnet
SOME TCP/IP PROTOCOLS
TCP/IP PROTOCOL SUIT
Application Layer
Transport Layer
Internet Layer
Network Access Layer
Telnet FTP SMTP DNS HTTP SNMP
TCP UDP
ARP RARP IP IPSEC ICMP IGMP
Ethernet ATMToken Ring Frame Relay
OSI
Open Systems Interconnection
developed by the International Organization for
Standardization (ISO)
has seven layers
is a theoretical system delivered too late!
TCP/IP is the de facto standard
OSI LAYERS
OSI V TCP/IP
STANDARDIZED PROTOCOL
ARCHITECTURES
LAYER SPECIFIC STANDARDS
SERVICE PRIMITIVES AND PARAMETERS
define services between
adjacent layers using:
primitives to specify function
performed
parameters to pass data and
control info
PRIMITIVE TYPES
REQUEST A primitive issued by a service user to invoke some
service and to pass the parameters needed to specify
fully the requested service
INDICATION A primitive issued by a service provider either to:
indicate that a procedure has been invoked by the peer
service user on the connection and to provide the
associated parameters, or
notify the service user of a provider-initiated action
RESPONSE A primitive issued by a service user to acknowledge or
complete some procedure previously invoked by an
indication to that user
CONFIRM A primitive issued by a service provider to acknowledge
or complete some procedure previously invoked by a
request by the service user
TRADITIONAL VS MULTIMEDIA
APPLICATIONS
traditionally Internet dominated by info retrieval
applications
typically using text and image transfer
eg. email, file transfer, web
see increasing growth in multimedia applications
involving massive amounts of data
such as streaming audio and video
Lot of applications have been standardized to
operate on top of TCP. Few are
SMTP
FTP
Telnet
MULTIMEDIA TECHNOLOGIES
TYPE OF TRAFFIC GENERATED BY
DIFFERENT APPLICATIONS
Elastic Traffic
can adjust to delay & throughput changes over a wide range
eg. traditional “data” style TCP/IP traffic
Adjust with congestion by reducing rate
Eg. Email, file transfer, remote logon, n/w mngt, web access.
some applications more sensitive though. Eg. FTP, web access
whereas, N/w mngt sensitive when problem occurs.
Inelastic Traffic
does not adapt to such changes
eg. “real-time” voice & video traffic
need minimum requirements on net arch such as assurance about
throughput, delay, no packet loss, no variation in traffic.
SUMMARY
introduced need for protocol architecture
TCP/IP protocol architecture
OSI Model & protocol architecture
standardization
traditional vs multimedia application needs
PRACTICALLY CHECK
IP UTILITIES
PING
TRACE ROUTE
IPCONFIG
TCP DUMP
NETWORK PROTOCOL ANALYSER
PING
Packet Inter Net Gopher
Determines if host is reachable?
Uses ICMP (Internet Control Message Protocol)
Sends two or more ICMP Echo Msgs.
Measures Round Trip Delay between two host.
Eg. Ping www.google.com
TRACEROUTE
Determine route that packet takes to reach the
destination.
Also gives latency & reachability.
Generally used as debugging tool.
Uses both, ICMP & UDP.
IPCONFIG
Display TCP/IP information about host.
Returns IP Address, Subnet Mask, Default
Gateway, DNS Host Name, IP of DNS Server,
Physical Address of NIC, IP, etc
Also checks DHCP is enabled for automatic
configuration of card’s IP address or not.
We can renew IP from DHCP.
Try:
Ipconfig
renew
NETSTATE
Provides information about network status of Host.
It provides status of:
Network Drivers
NIC
What information it provides?
# Packets
# Out Pkts
# Pkts in errors
Also provides information about
Routing Table in Host
TCP/IP Server Active
TCP Connection Active
NETWORK PROTOCOL ANALYZER:
WIRESHARK
Tool to capture, display & analyze PDU (Protocol
Data Unit) exchanged in a network.
Used for troubleshooting & to design new system.
Also used for teaching the operations of protocol.
Examining live traffic on network.
We can apply filters by
Frame Address
IP Address
Protocol
Combination
TCP DUMP WIN DUMP
NIC is set to promiscuous mode.
Card can listen & capture every frame that travels through broadcast n/w.
N/w, Transport, Application layer content can be seen, observed & analyzed.
To analyze these captured data, use Wireshark.
Eg:
windump –D
windump –i 2 –q –w c:\perflogs\diagTraces -n –C 30 –W 10 –U –s 0
Where,
i = #NIC selected
q = queue mode
w = prefix of file during creation
n = no hostname, only IP
C = size in million Byte
W = #log files
U = saved & written to o/p file
s = decrease amount of pkt buffering.
TWO CHAPTERS OVER,
TEST?
THANK YOU